


age is an irrational number

by valtyr



Category: Marvel Ultimates
Genre: M/M
Language: English
Status: Completed
Published: 2011-04-23
Updated: 2011-04-23
Packaged: 2017-10-18 13:55:28
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 8,749
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/189574
Author URL: https://archiveofourown.org/users/valtyr/pseuds/valtyr
Summary: <blockquote class="userstuff">
              <p>Steve and Tony grow old together.</p>
            </blockquote>





	age is an irrational number

**Author's Note:**

  * For [dollam](https://archiveofourown.org/users/dollam/gifts).



"Hello. Hello," Steve crooned at the baby in his arms, and it gave him a fierce look and flailed. "Sh, sh, your mommy is just there, look - " he tried to angle the baby so it could see Valeria Richards at the flower-strewn buffet, stocking up on tiny delicious foodstuffs, but it shoved a fist in its mouth and made a terrible face at him. "She won't be long." That was probably a lie, as she'd been buttonholed by a young Maximoff with a mouth full of quantum mechanics and flattery. Steve would never understand the courtships of the younger generation, although it was fair to say he hadn't been expert in his own.

Of course, in his day Miss Richards would have been a social outcast, and he wouldn't be standing here with an armful of squishy gummy baby.

That would have been a shame, really.

"You still have an arm, Captain?" General Danvers stuffed a toddler into his free arm without waiting for an answer, or even breaking stride, and made a beeline for Fury. Mahr Vehl followed in her wake, and winked at Steve.

"If it's no trouble," he said, and Steve waved him on somewhat awkwardly, trying to get the kid head-end up without resorting to throwing him up in the air and catching him.

The kid seemed to have inherited Grandpa Kree's sunny nature - or maybe the other parent back on the homeworld - he was pretty sure this one was Danvers' daughter's. She'd married a Kree, and her brother had married a mutant. Danvers had timed her pregnancies expertly to coincide with Fury's ascendencies, and reclaimed her job as soon as each kid was walking. Fury maintained it was all blind luck on her part. Steve reckoned sufficient luck was indistinguishable from tactical brilliance, and anyway, she seemed a lot happier than Fury so who was the smart one here?

Fury's voice was rising, and Danvers had her hands on her hips in the attitude that meant she didn't give a hoot if Fury was shouting; Steve decided it was time to take the kids outside, before they decided shrieking was today's game and the wedding reception became a disaster area. The bride was due to make her appearance soon, which would hopefully end the fight for the time being. He suspected he knew what it was about, and and it was going to last for weeks.

He sidled out on to the verandah, and looked down the path towards the fountain, where the Stark brothers sat on a dark stone bench like a mismatched pair of bookends.

Steve squinted at them, tried to see them as strangers for a moment, rather than his husband and his brother-in-law. Gregory looked a bad forty-five, Tony a well-preserved sixty. They were both just over seventy.

Gregory, despite having successfully married off his eldest granddaughter to a man hotly tipped to run for President in 2054, looked sour. Tony looked smug. All normal, then.

The verandah door slammed open, and Fury emerged on a wave of violin music and applause. Steve should really go in and say something nice to the bride; Alicia was a sweet girl. Still, she was also sweet enough to consider baby-sitting a good excuse for absence. He'd take her for a waltz later.

"Danvers claims to be retiring," said Fury in undertones of furious outrage. He'd already disposed of his bow tie somewhere, and his buttonhole was missing most of its leaves. Steve sincerely hoped he hadn't had a fistfight with Danvers. "What's she up to?"

"I think she's retiring," Steve said placidly, disentangling toddler fingers from baby shoelaces. "She said she was done."

"You're never done with this job."

"I hear she's going to live on the Kree homeworld, as a liaison."

"Leaving this job is practically treason."

"She also said if she quit while on top, instead of waiting for you to push her out again, it'd bug you for years."

"Ha!" Fury seethed for a minute. The baby squawked, and he tickled it under the chin; it grinned at him. Babies, inexplicably, tended to like Fury. "Whose kids are these?"

"A Richards and a Danvers."

"Captain Babysitter."

Steve shrugged.

Fury's phone buzzed; he tapped the piece in his ear, and then scowled.

"The fuck, Stark, am I your secretary? He can manage a phone and a baby, or can't you buy your boytoy a handsfree kit?"

Steve ambled down the steps and path, to where Tony was smiling at him. The baby cooed enthusiastically at the glittering concoction of water and obsidian edges that was the fountain, and Tony took the squirming infant from his arms and held it up so it could grasp fruitlessly at the rainbows forming in the bright sunlight. Gregory promptly snagged the toddler, and gave it a suspicious look. It was not entirely impossible he'd push it back at Steve and try and grab the baby from Tony; but he apparently deemed walking and talking made his small child the superior option.

This close, he could see the tiny stiffnesses in Gregory's face, the marks of surgery and chemical treatments that made him look so much younger. He was vaguely aware of all the action beneath the skin, the biochemicals that kept Gregory's body young; some of them had been developed from Steve's own unaging physique.

"Gregory was just telling me I should get Botox, keep myself young, or my trophy husband would stray," Tony batted his eyelashes; Gregory rolled his eyes. "What do you think?"

"I don't recall loving you more when you were younger." Once Steve would have responded with gritted teeth and awkwardness, but they'd knocked the corners off this thing decades ago. Tony liked to play up the billing and cooing in front of Gregory, who had had two marriages and closed both down like defective projects. That competition was a decisive win for Tony, and Steve had no real objection to helping him rub it in.

"I was prettier." Tony grinned, the fans at the corners of his eyes deepening. "Wasn't I?"

Steve put his thumb over the lines, stroked back into the white at his temples; Tony was ageing more gracefully than he'd done anything else in his busy life, which was an example of cosmic injustice, considering all the things he'd put his body through. "I don't think so," he said with perfect sincerity.

"It strikes me as particularly amusing that eternal youth belongs to a man who's largely indifferent to it." Gregory's eyes wandered over him with familiar acquisitiveness; as Tony's perennial favourite, Steve had grown used to the covetous looks, and considered them no more worrisome than the looks he cast at Tony's new cellphone; he was never going to try any of what Steve might describe as _funny business_.

"Oh, he's only indifferent to it in other people," Tony squeezed his wrist and pressed a kiss to his palm. "We'd soon hear him squalling if his knees started to ache."

"How are the kids?" Steve tried to turn the subject. Gregory scowled. Tony grinned wider.

"Carmine's going to _art school_ ," he confided in a hushed tone, and Steve could hear the grind of Gregory's teeth. "Such a shame! A real talent for astrophysics, that one, offered an internship with the Kree, but no, she wants to be a sculptor." Tony gave the baby his cellphone to play with; unsurprisingly, at six months, _play with_ meant _eat_.

Steve tried to look appropriately surprised and sympathetic, rather than like a man who'd actively abetted his favourite grandniece. _Follow your heart,_ he'd told her, and she'd snorted and turned those sharp blue eyes on him. Her hair was red, like her mother's. _I'm too old for cliches, uncle Steve. You can't tell me you never regretted it._ He'd showed her Gail's photo a few times, with no sense of guilt; Tony was a gracious victor and had never grudged the part of his heart that would always belong to her.

 _I regretted it a thousand times_ , he'd said slowly. _But there's a comfort in knowing you chose your own mistakes, and at the end, I won't have anyone to blame but myself. It's my own work, my life. I hope you'll be able to say as much._

Hard to tell if his advice had made a difference. She was a contrary creature, with all Tony's endearing charm and Gregory's ruthlessness.

Tony poked at the baby thoughtfully as it gnashed its gums on his phone. Gregory was staring at the toddler as if monitoring it for art-school tendencies. Steve watched them both, keeping an eye out for sudden sharp objects, poisonous substances, or explosives. You never knew, with Starks.

The baby sneezed, and Tony wrinkled his nose. Gregory gave him a smug look. Steve retrieved the baby, and found a tissue for its nose, and it snuffled and bubbled at him.

"So what are you two plotting now?" A simple enough conversational gambit, but Tony and Gregory exchanged a fleeting glance that rang alarm bells. "This had better not be anything that's going to upset Alicia."

"I'm hurt," Tony gave him limpid eyes, "Wounded that you would think me capable of disrupting that dear child's special day."

"I'm throwing this party, anyway," Gregory glared at them both. "If I want to do something, I will."

Steve looked from one to the other. Guilt, guilt, all over their faces.

"I will be watching you both," he warned, and plucked Danvers Junior from Gregory's hands and turned back to the Mansion.

 

 

Gregory stayed at their place, which Steve appreciated. Gregory present at breakfast meant Tony would be in the mood _before_ breakfast, just to demonstrate he was still capable of wrecking Steve. Steve was quite ready to be wrecked; if there was a tiny sneaking regret associated with Tony's age, it was the decrease in his sex drive.

Where Gregory used biology to delay age, Tony used technology to compensate. Steve pressed his face into Tony's shoulder and whimpered shamelessly as the toy inside him pulsed like a heartbeat, and Tony ruffled his hair.

"You like that?" Voice soft and caressing, the sound of it ramping Steve's arousal higher, those coaxing tones that were only Steve's. "Of course you do. Want it bigger?" Steve made a choked noise, unable to form words, and Tony did something to the remote and the reactive gel reshaped inside of him, swelling, and oh God Steve wasn't going to be able to sit at breakfast -

He came again, the fourth time, practically dry, and lifted his head enough to be kissed deep and slow.

"Okay?" Tony stroked his cheek. "Want me to take it out?"

"Not yet." Steve shut his eyes. The deep stretch in his ass still felt good. He let his heartbeat steady, Tony's hand petting idly through his hair. "So what's Extremis?"

He slitted his eyes open to see the slight rigidity that meant Tony was hiding; Steve scowled, and Tony narrowed his eyes. Attack, then.

"Steve, I seem to recall something about trust in our wedding vows." Tony affected hurt, and Steve arched his eyebrows, not fooled at all.

"And?"

"And so hacking into your husband's - " Tony stopped. Then he sighed, and smacked himself in the forehead.

"Hm?" Steve raised his eyebrows, concealing his glee. Just a few seconds delay on Tony's responses after getting laid, but it could be enough.

"You didn't hack my systems, did you?"

"Of course not. I hacked Gregory's last night after you two went to sleep." Gregory should know better than to leave his laptop locked in the safe in his limousine in his brother's high-security garage. "I wasn't sure you were in on it until just now."

"Excuse me, that work could not have been anyone else's." Tony pinched his rear; Steve tried to squirm away, and made a choked noise as the toy shifted inside him.

"That fatality rate looked more like one of Reed's projects," he forced out, and Tony pinched again, and Steve couldn't help rocking his hips against Tony's thigh.

"Excuse _me_. That project was impossible. I've managed to get that to a point-zero-one chance of success in less than a decade."

"Why?"

"Because science," Tony said testily. "It's very advanced. You couldn't understand." He put his fingers on the tip of the toy where it emerged from Steve's body, and light pressure set sparks behind his eyes. It was a second or two before he could gather words.

"Unless a scientist experienced in both AI and biology explained it to me." Tony's hand froze; his lips tightened.

"You spoke to - "

"We video conferenced. She says hi; all the kids are doing well, and - "

"I'm sure." Tony shook his head. "And did this rate Her Majesty's attention?"

"Wanda wasn't available to talk, but Jan said that she might be willing to enhance the chances of a positive result."

"For a price, of course." He blew a raspberry, which was his way of expressing great respect for the iron hand inside Wanda's still-velvety exterior. Twelve children and twenty-eight grandchildren and one great-grandchild in the royal family of Nation X; Steve was happily anticipating a new crop of little mutant babies to play with very soon. Wanda's policy of outbreeding the flatscans was one she enthusiastically embraced for her own family.

"But why are you doing this? What happened to not wanting to live forever?"

"Living forever's a side-effect, really. All the efforts to find immortality running through your veins, and this turned up in an genetic computer interface. It was Gregory." Tony shut his eyes. "He was halfway there... but there's no elegance in his work, he relies on force and numbers, but he wants this for himself. Which means the success rate has to be in the high nineties before he'll try it. He needed the impossible, in five-star comfort."

"So he came to you, of course, but why did you say yes? Feeling your age at last?" There had been more things, lately, Tony grimacing in the mornings, taking too long to recover from hard missions, but... Steve had been looking forward, vaguely, to Tony retiring, to be safe at home. Not that he wouldn't miss Iron Man at his side, but there would certainly come a time when it was safer for everyone for Tony to stay home.

"I was resigned to death with the tumour, Steve. Every day since then was a gift. And I like to think I've taken them that way. No, it's..." He opened his eyes, and ran his gaze over Steve's body, which looked almost exactly the same as it had done during World War II.

"It's me?" Tony nodded, and Steve blew out an exasperated breath. "You know - "

"I _know_." He put a finger over Steve's lips. "Don't think I'm not delighted, that you barely even notice I'm wrinkled and grey and my joints click. Because you love me."

"It's normal, Tony. People grow old together all the time."

"But you're not." Tony waved away his protest. "That's not the point, anyway. The point is, you may not notice I'm old, but you're certainly going to notice when I die."

Steve's throat seized, for a second.

"Not for -"

"Practically, the natural human lifespan can be coaxed out to maybe a hundred-thirty."

"Another sixty years," Steve said with some relief. Tony could certainly afford the very best medical care, and even if he somehow bankrupted himself, he was Steve's husband and therefore had SHIELD coverage.

"And I have every confidence you will stay loyally by my side and be genuinely baffled by anyone who suggests you might prefer someone who doesn't need adult diapers."

That went without saying, of course. Tony was Tony, and Steve loved him, and that had all been settled years ago.

"But that just pushes the problem forward, doesn't it? What will you do in sixty years, Steve, when you're young and strong and beautiful and alone, and I'm smoke on the wind?"

"You want to be cremated?" Steve focused on that. He'd assumed there would be a grave to visit when... it happened. He still visited Bucky and Gail at least once a month.

"Flying, yes, and I think I've left sufficient mark on the world a monument would be overkill. Don't change the subject. What will you do?"

Alone, without Tony. Without anyone, by then; Jan and Wanda and Clint might last a little longer, but they would all proceed into their graves, and he would be left all alone -

The children, of course, he'd keep an eye on them, but they'd die in their turns, and they couldn't keep passing him down like some kind of family ghost.

They'd die and disperse and scatter, and Steve would go on unchanging and alone.

Except for Fury, of course.

"I don't want to leave you alone, darling," Tony murmured. "You're so terrible at it. You'll end up collecting stamps and calling in to radio shows to complain about young people."

"I'm not," Steve lied, dry-mouthed. "And even if I were, I don't want you killing yourself with this - "

"I have years and years." Tony squeezed him. "There's no hurry. I'll get that success rate up."

"But Gregory - "

"My brother is convinced we can get it all done in a year. And he said that five years ago. Steve. It's all right. I have no motivation to take terrible stupid risks, all right? I want to stay right here with you."

"I worry, Tony, I - ahhh," Steve bucked his hips involuntarily as Tony's hand moved back to the remote. "No, that's cheating - "

"I have to take the advantages I can," Tony said, and slapped Steve's ass. "Up on your hands and knees; I have some functionality I want to test - "

Worry receded under the warm tide of lust slipping over his body. He put his head down and panted, and decided to forget he'd ever heard the word _Extremis_.

 

 

Tony caught the baby's cold, of course, and spent three days confined to bed, sneezing disconsolately while Steve brought him soup and orange juice and ignored his pathetic requests for hot toddies and coffee and laptop. It was only a cold, but Tony was not exactly known for taking good care of himself, and turning a cold into pneumonia would be just like him.

On the fourth day, Steve granted him couch and laptop access, and snuggled up beside him with a book. Reading with Tony's hand carding absently through his hair was always a pleasure, and it meant he could listen to Tony's breathing for telltale rattles. You really couldn't be too careful.

Sixty years, Steve thought, and resolutely turned his eyes to his book.

Twenty minutes in, Steve's phone went off. Any vague hopes of a friendly chat or a request to babysit died when Fury's name appeared on the screen.

"Tell the old boy you've caught my cold," Tony suggested loudly enough for the microphone to catch, and Steve held the phone to Tony's ear until Fury had done cursing at him.

Fury had a foreign mission for them, and that made Steve uncomfortable. The Ultimates, as a team, rarely left the US. The last time had been chasing down a rogue Nation X mutant, and Wanda had pulled the strings for that. Whether the strings were attached to people, or the fabric of reality, he wasn't sure.

"It's not interfering," Fury said, voice too loud for the phone. "They've requested help. And _because_ they requested help, we are going to send our best out and be extremely helpful and not invade anywhere, because the United States is a helpful neighbour who just want to do good in the world."

"He's got that written on his palm in marker, I've seen it," Tony contributed, and Steve gave him a stern look that didn't faze him at all. The more they interacted with alien nations, the more Fury seemed to shift his allegiance to humanity as a whole, rather than America, and Steve was inclined to encourage this development.

"We go there, punch some sharks, accept their thanks and come home clutching straw donkeys and postcards."

"My kind of plan." Steve rolled onto his back and looked up at Tony, who raised his brows expectantly. "Tony's still benched, though." Tony stuck his tongue out, and Fury growled.

"He does this on purpose. Take War Machine." Tony huffed, and tapped pointedly at his keyboard, the usual signal for _I am doing very important work nyah_.

Steve sat patiently through a conspiracy theory about how Danvers had retired to foment rebellion among the mermaids, and then hung up and cuddled up to Tony.

"The War Machine is terrible at underwater work." Tony scowled at him. "You'll miss me when - "

"I'll miss you all the time." Steve kissed his temple, not-so-subtly checking pulse and temperature, and Tony's mouth twisted in the way that meant he was trying to stay annoyed. "And War Machine's not _terrible_. There's a big gap between terrible and not as good as Iron Man, you know."

"And don't you forget it. I'm not giving up my place on the Ultimates to Gregory's off-brand knockoffs. Call me if you need support." Steve made a face. _Of course I will_ sounded like an easy lie, but he knew in the moment where he crunched the numbers and made the calls, he'd drag Tony from his death-bed if he judged it necessary.

He was also smart enough to know letting Tony risk his life was much better for his overall well-being than Steve's preventable death would be. War Machine wasn't too bad, though. This one had only been in the suit four years, but he was doing well enough. There would be no call for Iron Man.

"It sounds like a simple job," he said instead. "You'd just get bored and start showboating."

"You're jinxing it now." Tony gave him a kiss, and turned back to the screen. "Hurry back."

The job _was_ simple, though; an undersea Soviet-era gadget that had turned on when it shouldn't, and driven the denizens of the Red Sea into near-madness with the mysterious electronic signals it sent out. This was possibly a side effect, as the other effect was to interfere thoroughly with radio waves for a radius of several hundred miles, which was causing an awful lot of disruption. Underwater fighting wasn't Steve's favourite thing, but the team was trained in it and it all went simply enough until Black Widow got her hands on the offending gadget and turned it off. At which point, sharks, jellyfish, fanged glowing monstrosities and octopodes all lost interest and swam clear.

Steve came up from his dive fast enough to catch the edge of the small boat, and flip himself into it; he yanked up Hawkeye, who was one of Clint's proteges, and Black Widow, who was one of Gregory's, and Shatterstar, who was an alien. Mahr Vehl had deposited him on Steve with the same faintly apologetic look he used to dump children and grand-children on him. Shatterstar was probably less trouble, on the whole.

They climbed the rope ladder to the ship's deck, and Shatterstar politely handed him over the rail before making a beeline for Fury. He still seemed to feel Fury would produce extra missions if stared at hopefully enough. Steve loosened his rebreather, swept a little of the water off himself, and glanced around.

Something was very wrong.

The ship was silent; only engine noises and the slap of waves on the hull. None of the normal chatter, and the deck was almost empty. Only Fury, under the canopy, standing by the table he'd used to spread out the briefing before they left.

But the briefing papers were still there, and that wasn't right; Fury was passionate about his data security, and the papers should have been shredded and then loaded into the incinerator. That meant something. The team were staring down at the papers laid out there, with stunned expressions. Had the mission failed, somehow?

No, if the mission had failed, there would be curses, and sighs, and people would turn to Steve. No one was looking at him, and what kind of news would cause people to rigidly refuse to look at him? Even Fury was looking down at the table.

Steve stepped up to look down at the papers.

Photographs, mostly. Large, clear, glossy. The Iron Man in flight, facing - something, somebody. An air battle. Tony, versus - someone. Someone flying. A mutant? Male, dark haired, medium build. He looked perfectly normal, baseline human, except he was flying. And here, the was shooting little glowing darts from their hand, and here, he was crushing one of the Iron Man's gauntlets in his bare fist.

Steve blinked at that. The armour was tough, but it had crushed like a soda can, and Tony's hand had to be broken, and broken bones were serious when you were Tony's age.

Other pictures, fire and impacts, and the armour peeling and buckling, the armour was red where it should be gold. Hard to tell exactly what was happening, there was smoke...

There was a report lying in front of Fury. He fumbled it up with numb hands, turned to the final page.

"He's - " Steve lifted his eyes to Fury, whose skin had an ashen cast. Fear, Steve noted dimly. Fury was afraid.

"Went down over - " Fury's voice was gentler than Steve had ever heard it; he spoke over it.

"Why was he out? He's sick!"

"He had a cold, not - "

"He wasn't supposed to be out!" The Black Widow stepped delicately back from the table, and Hawkeye had her gun in hand. Steve's brain seemed stuck, somehow, as if he could insist on the rules and so Tony wasn't out so he couldn't have -

He took a deep, slow breath. Tony had gone out. He scrabbled blindly at the report, and checked the details. Some stupid cult who thought the end of the world was due, taken over a Stark facility - it took Steve a moment to puzzle out they meant one of _Gregory's_ facilities, and they'd taken Gregory himself hostage which of _course_ meant Tony wouldn't wait, he'd go charging in to rescue his twin.

"What happened?" He'd just looked at the report, but somehow the details were sliding away. He looked down at it again, tried to focus. Too many question marks over just what had taken down the Iron Man.

"The suit reports said massive internal injuries," Fury said slowly. Steve's hands had started to tremble; he dropped the report, and then put down his shield. Then he sat down, expecting to land on the deck, but there was a chair there. He nodded thanks to Shatterstar, who was standing close against his shoulder; Shatterstar wasn't afraid, of course. He was still puzzling out what had happened. Steve should explain it to him. Not now. "He went down near the facility; it's possible they went out - "

"They'd have no reason to treat him, even if they had the means. Which they wouldn't, if it were a pure research facility. Why was - " he snapped his mouth shut. It was all perfectly simple and the conclusion was always the same.

Tony was dead.

He would have been almost dead when he landed; the suit's life support was keeping him breathing, but the internal bleeding would kill him rapidly, he'd been torn apart by - by that person. Whoever he was. Crammed to the gills with Gregory Stark's bioweaponry - an apocalypse cult, death or glory. If there was a whole group of them - no, with the success rate there couldn't be more than a few of them surviving. He blinked, and looked down at the pictures, Tony's blood smeared all over everything, spattering the face of his attacker. Contorted in fury, but he was no one Steve recognised and who hated Tony? No one hated Tony. Even the people who _did_ hate him still liked him, grudgingly.

"Cap." Steve opened his eyes, only then realising he'd closed them. There was a mist in his eyes. "That means there's someone, maybe multiple someones, running loose in the US capable of taking down the Iron Man."

"We - " Steve swiped away tears, but more came. Well, never mind, they could stay. He didn't need to see clearly now. "Right, we'll - a helicopter?"

"Got a jet on its way; ETA twenty-five minutes. You'll be all right?" Fury's colour was more natural now, his posture relaxing.

"Sure. Yes."

The team watched him with cautious tension as he sat quietly. Even Shatterstar seemed to have gathered that something was wrong with Steve, and kept his gaze fixed on him. Widow and Hawkeye would have heard about the time he went rogue, of course - he'd heard they ran training simulations on it, What To Do If Your Super-Soldier Loses It, but this time, there was no need. His goals and SHIELD's goals were perfectly aligned; whoever had killed Tony was going to die.

He smoothed out the report, and bent his head over it. As the details came into focus, the dampness in his eyes cleared up. There would be time for mourning later; Steve had nothing but later, now.

 

The plan was simple enough. Steve would lead in the Ultimates and fight the guy. Fury would take his Avenger team and try to recapture the facility. If Gregory Stark was alive, he'd know the secrets of the Extremis.

It was a holding action, nothing more; every time they had him locked down, he'd display some new power, and the odds would tick over in Steve's mind and the plan repattern itself. Thor, he wished Thor was here, Thor loved Tony and would be happy to join their revenge, and Thor's overwhelming force was what they needed here. Black Widow was down and out because this guy had _breathed fire_ , and really -

He was too fast, that was what it was. He moved with blurring speed, not as fast as Pietro - no one was as fast as Pietro - but it was too fast for a normal human to register and respond, and that had to be what had killed Tony and might have killed the Widow.

That was why Steve was going hand-to-hand with him when he should be backing off and running this operation, because almost half a century of combat combined with his enhancements meant he didn't have to think about this stuff, it was all by rote. He could have done this with his eyes shut, because this wild-eyed idiot didn't know combat from a hole in the ground, he was relying on being superfast and superstrong and near-invulnerable, and to Steve's mounting fury his fists were beginning to ache from punching him.

They couldn't use a nuke here; he'd survive getting hit with a tank or plane; he could fly; he seemed immune to impact damage.

Blades, time to try blades. EMP, maybe. He was immune to his own gases, but maybe something that wasn't his. Could he drown?

Was he simply mutating to meet every need, like the Hulk did?

They needed to know what this thing - person - was. And that meant re-taking Gregory's facility, and that meant keeping this monster occupied so he couldn't defend it, so Steve kept moving, kept planning.

He tired of fighting Steve - he hadn't landed a blow on anything but the shield in five minutes - and rose into the sky. Steve gestured, and the team set up another perimeter, and another arrow-flare arced into the air to mark their position. This Hawkeye enjoyed her archaic toys.

"Get some EMP arrows up for Hawkeye," he ordered through his comm. "See if you can get hold of Quicksilver or Speed." Wanda didn't like mutants of Nation X giving aid to foreign governments, but they might make an exception for this; Speed had always nursed a distinct admiration for Tony's cavalier ways.

"Support incoming," Fury snapped in his ear, and while he said other things, Steve didn't hear them, because the Iron Man slammed bodily into the airborne monstrosity

Steve kept moving, yelled _bring him down_ and drew his knife and saw Hawkeye rack a barbed arrow, and armour and man spiralled through the air and Steve hated himself for the hope. The armour was fitted to Tony in the minutest of detail, no one should be able to wear that armour with such ease, fly it with such grace, every fibre in his body sang _Tony Tony Tony_ but -

It was Tony, he knew it was Tony.

It moved with racing speed, though, dodging the blows and grasping hands, too fast for Tony, but no one else could be that assured in the air. _Rhodes_ , Steve's memory spun up, but Rhodes had retired on the dot of sixty. He might have been dragged out of retirement, but surely he hadn't been that fast either -

Maybe Tony had upgraded the armour and not told anyone?

Iron Man plummeted earthwards and smashed the guy into the concrete before zooming skywards again - probably he'd heard Steve calling for EMP - and Hawkeye put three arrows in him and Steve came in with the knife, but he rose in a charred ground-up mess and slashed at Steve with a handful of claws before screaming on a note that made Steve's head swim.

Still, Steve's body kept moving, engaged, hit the asshole with the shield and kicked him in the nuts and jabbed knuckles into his throat, and he actually reeled, staggered a few steps back and that was the first sign of weakness they'd seen in him.

" _Get him_ ," Steve yelled hoarsely, not his greatest plan, but Hawkeye's next arrow smoked and pierced and let out a dull _thud_ as some kind of explosion went off inside him. Steve's heart leapt, but then the guy staggered into a run and took off and made for the clouds, and he was in retreat but he was going to get away - arrows chased him, but Hawkeye was too conscientious to use the really damaging gear unless she was sure of a hit.

He was almost at cloud cover when Iron Man dropped into view, and held out his palms. It wasn't a repulsor that went off; it looped and swirled around the man's body, crackled around his skin, and he screamed, a hoarse animal sound. Iron Man free-fell towards him, still streaming the sharp blue crackling energy from his palms, and when his gauntlets locked onto flesh the jetboots kicked on. They dived together at punishing speed, and Steve threw up an arm to block the inevitable impact of metal on concrete - but Iron Man pulled up less than a foot from the ground; which meant the man he held in front of him was left a dirty smear across the parking lot, as Iron Man climbed skywards for a victory loop.

Steve dutifully checked the corpse, which was going nowhere. Then he turned off his comm and ran. He ran as fast as he could to meet the armour as it came to land with the skipping step that Tony always landed with. He didn't quite lift the armour off its feet with the force of his hug, but the shoulderplates scraped noisily against the backplate, and he'd probably scratched the paintwork but he didn't care. Iron arms slipped round his neck, and Steve dipped his head for the kiss as the faceplate lifted away.

Then he shied away, fast, ducking out of the grip and bringing his shield up.

"What?" said the young man in the armour in familiar tones. Neat goatee, sharp blue eyes, but that was _not Tony_. A Stark, possibly, but not Steve's Stark. "Steve?"

"Who the hell are you?" he lashed out with the shield, knocking the armoured figure off balance, and followed it up with a kick that swept his iron feet out from under him, at the cost of a hell of a bruise on his shin. " _Where's Tony?_ " It felt like the floor had fallen away, leaving only the shocking drop with shattering at the bottom. Not dead, not dead, please -

"It's me," the man - the _kid_ , he was barely out of his teens - one of the younger Starks, maybe, but Steve _knew_ all of them. Did Gregory have a concealed family somewhere? He raised his hands placatingly, palms turned together instead of towards him, because empty hands from Iron Man were a threat. That was a Tony gesture, Steve noted numbly. "It's me, Steve, I - "

The growing chatter of helicopter blades drowned his voice, and Steve half turned towards the landing copter. Fury jumped down, followed by an inelegant scramble from Gregory, who was battered and bloodstained and looked torn between rage and glee.

"Please don't kill Tony." Fury strode towards them. "We're hoping to get quite a few more years out of him."

"I need blood right now," Gregory snapped. Steve wondered vaguely if he was a vampire, now. Why was Tony - Tony was - he was _young_.

"I don't understand," and it was a lie, Steve's brain had already sorted all the data and was presenting him with the Extremis technovirus, and of course, Gregory's priority was blood samples, rather than thanking his rescuers. "What - Tony?"

Tony gathered his feet under him, eyeing Steve's aggressive stance cautiously.

"It was a gamble," he allowed, and armour fell away from his right arm to let Gregory fasten on with tourniquet and needle. The first human trial, Steve thought - no, the second, but the first was reduced to a greasy smear. "They stripped the armour and threw me in with Gregory. And I was virtually dead. So."

"And you happened to have the Extremis on you?" Steve looked incredulously at Gregory, who shrugged.

"It seemed the best place to hide it. You'd be amazed how many otherwise unstoppable terrorist groups get all bashful at body cavity searches. I've still got three Flash drives - "

"I always said Gregory pulled his solutions out of his - "

"Why didn't you take it yourself?" Steve snapped.

"Because it kills most of its subjects, and I was planning to get out alive." Gregory scowled at him. "There are almost three hundred corpses at the facility which demonstrate just how lethal Extremis is; they were destroying all the studies and samples in an attempt to prevent it being duplicated."

"Which is ridiculous." Tony grinned up at Steve. "Captain America's brother-in-law is going to be well aware of the importance of keeping multiple copies of your notes."

"After spending half my career trying to duplicate another scientist's work, I'm not having mine lost so easily," Gregory agreed, and Tony pouted at him.

"Ours, Gregory. _Our_ work." Gregory turned the scowl on Tony.

"I am strangely unsurprised you lived through it."

"I was born under a fortunate star. If you hadn't been in such a hurry to be born, it might've been you."

"That's right, Tony, you keep explaining how second place is better, really. One day, maybe you'll come to believe it - "

Steve had to believe it; that was the the Stark twins.

 

 

Steve changed out of his uniform, took a shower, wrote a report, and then stormed around the Mansion with a feeling of baffled rage. He didn't know - it was all - Tony was alive, though. Steve really wished he could get drunk.

He fetched up at the workshop door, where Tony was stripped down to his tight black boxers, drinking a Martini. For a moment, from the rear, with his iron-grey hair, it was as if nothing had changed, and Steve's heart ached and he took a step forward, and Tony turned to smile at him.

It felt somehow treasonous, the way his body perked up at the sight of Tony's smooth skin and sculpted muscles, younger than Steve had ever seen him.

"You still have grey hair," he said gruffly, and Tony's smile widened.

"I think it'll grow in black," Tony ran a hand through his hair. "It does look a bit out of place, now, doesn't it?" He gestured at his body, and Steve coughed and looked at the armour. He'd _never_ seen Tony like this, Tony had been over thirty when Steve met him, although he wore it well. This Tony looked younger than Steve did. Unfair to call him barely legal, but Steve wouldn't be surprised if he got carded.

"The armour looks different."

"It was damaged in the attack; I had to make field repairs. You wait, though, the next iteration is going to be _special_. You are not going to believe the things I can do now." He waggled his eyebrows. "Speaking of which, I didn't get my kiss."

"Right." Steve leaned in obediently, and soft firm lips were... different, somehow. Tony purred and pressed closer.

"I don't - " Steve shifted away from Tony's hand. "You're - " he lifted a hand to touch, and then didn't want to, and ended up waving a hand vaguely over Tony's cheek.

"I thought you loved me despite my wrinkles, not because of them," Tony said a little waspishly, and looked down at himself. "I could maybe reprogram, for wrinkles? If you like."

"No, I..." Steve shook his head. "It's so different."

"You didn't mind when Gail put _on_ fifty years overnight," Tony said in an edged voice, and Steve swallowed a retort that would have made it all worse.

"We've been together an awfully long time, Tony."

"Yes?"

"And for most of that..."

"I've been old, right."

"Not... well... older," Steve temporized. "Not like this."

"Is this a fetish?" Tony had assumed an expression of detached amusement. Steve was pretty sure that was hiding hurt.

"It's not - Tony, you've undergone a major physical change, I don't think it's wrong to want a little time to get used to it!"

"Steve - " Tony put his hands over his eyes, and gritted his teeth. "Darling. Run along and have an angst about this on your own time, will you? I have important science work to do."

"Sure you do."

"I mean, I'd _rather_ be getting laid, but - "

Steve closed the door to the workshop with great care. Slamming it would have been childish, and despite appearances, they were both old enough to know better.

 

He retreated to their bedroom, and dug out his photo album. He owned digital frames, and of course Tony had a well-organised album on the server tagged in a hundred different ways, but Steve liked physical pictures, liked turning the pages and putting his nose close to study the pictures in detail.

He propped it on a pillow and rested his chin on his hand, and slowly paged through.

Even in the earliest pictures, Tony still had laugh lines. Steve _liked_ the laugh lines. When he'd first - well, perhaps the second or third time he'd seen Tony, when he'd been convinced it wasn't a Nazi plot - anyway, he'd warmed to Tony because of his smile, his laughter, and and the creases at his eyes proved that he wasn't acting, he was a man who laughed at the world. Steve would've liked to have been a man like that.

It had taken Steve quite a while to figure things out, and Tony had been reasonably patient with him, and Tony had been almost forty when they married. Steve could vividly remember finding the first grey hair, and staring at it in bewilderment. _Wedding planning_ , Tony had joked. _Pepper almost drove me into my grave, and I still don't know what font we used for the invitations._

Alexandra Zeferino. Steve still had one of the invitations stowed away somewhere. Maybe he was too sentimental. There was one of Iron Man carrying Cap, and it was like a hundred other pictures except the sky was perfect cloudless blue and Steve was smiling, his shield raised to shade his eyes so he could look at the golden faceplate.

"That model of the armour sucked, you know," Tony's voice was too close, and Steve twitched before he could stop it. Tony shouldn't have been able to sneak up on him. "Sure, it was faster, but it steered like a cow and gave me an ache in my lower back."

"It's a nice picture."

"You look happy." The bed creaked, and Tony straddled him. Steve didn't look round. "Flip to the end."

Steve silently turned to the last page, which had a photograph from last December, Tony sitting in a high-backed chair with Steve at his feet. That one was in there mostly because Felicity Stark, eight years old, had taken it. She was a spoilt adorable brat and had made Steve promise it would go in his album.

"Seventy-three there," Tony said, like Steve didn't know.

It was like cheating. He'd loved Tony's body, even as it softened and the skin crinkled and the hairs turned grey, he had genuinely loved it and never looked at anyone else, hadn't wanted to, and now Tony was lean and sleek and beautiful, and wanting him felt like a betrayal. And he did want him; Steve's body had apparently grasped that this was for him, and his heart was beating fast and he was hard inside his jeans just from the weight of Tony's body on his.

When they'd first started dating, Tony had _always_ wanted sex. Two, three times a day, and Steve had been on a near-constant high from sheer endorphins. But he hadn't minded when it ran down, every relationship slowed down a little and Tony was older and he hadn't _minded_.

Tony breathed down the back of his neck, sending a shiver down Steve's spine.

"I thought you were dead," Steve blurted, and Tony went still. "They said you'd gone down with massive internal injuries - I thought - "

"I'm fine." Tony slapped his hip. "Roll over. Shut your eyes."

Steve shut his eyes obediently, and squirmed over under Tony's weight. Tony didn't comment on the bulge in his jeans, just settled down astride him, arms resting on his shoulders. The scrape of his beard, the warm familiar scent of him, the just-right weight on his thighs.

"Oh," he put his hands on Tony's hips, which hadn't really changed. "I thought you were dead," he said again, but this was Tony in his lap. Warm lips on his, the easy strokes of his tongue, and Tony was alive and safe and in his arms. He yanked him close, wrapped him in a tight embrace, and he could ignore the difference in skin and muscle with Tony's smell in his nose and that comforting voice murmuring to him. "I love you."

"Love you too," a whisper, and the difference in timbre was almost imperceptible when he pitched his voice low and soft. Steve ran his palms up Tony's back, testing, and really that wasn't so bad.

He could get used to this.

He spread his legs in invitation, and then thought of Tony's hips, and tried to remember the last time he'd been inside. He tugged Tony's boxers down and nudged up, hopefully.

"Oh yeah," Tony had lube, somehow, and he smeared Steve's fingers and took them in easily, tight muscle relaxing sweetly under Steve's touch. "Jesus, how long has it been?"

"A couple of years," Steve touched him lightly, and then more firmly when he writhed and panted.

"I missed doing this. You missed it?"

"No," Steve said automatically, and flexed his fingers against the slick tight channel to hear Tony's breath rasp. "Well. A bit? Just a bit."

"How long since I've ridden you?"

"Too long," Steve felt his cheeks flood with colour, and then Tony pulled off him and unzipped his jeans, pulling his cock free with no hesitation or teasing. Wonderful encompassing heat, and Steve grabbed for the sheets and tried to keep still, and then realised he didn't have to anymore, and bucked up into Tony's body.

"Yes, Steve - fuck - " Tony threw back his head and shuddered and came, and Steve blinked up at him as he snickered. "Oh damn, now I have premature ejaculation issues? I really am young again. Don't look at me like that!"

Steve grinned back, awkwardly, and reached for Tony's cock. If he _was_ young again - sure enough he hardened nicely under Steve's hand and soon he was squirming and gasping, each jerk of his hips sending a jolt of pleasure through Steve's body. Tony knocked his hand away and rode him, and it was fantastic, his hips rolling and soon he was breathing hard but he kept going, thigh muscles flexing under Steve's palms. He just kept _on_ going, no sign of fatigue or aches, and dear God that was good, Steve rose to meet him again and again, and Tony came all over his belly and shook and mumbled "Don't stop."

"You sure?" and Tony planted his hands either side of Steve's head and kissed him messily.

"Come on, Steve. I want to _ache_. Do you know how long it's been since I had a _good_ ache?"

Steve obediently set his feet and began to thrust up into him, slow and steady, except Tony glared at him and pushed back pointedly until he stepped up the pace. And then again, and then he was digging his fingers into the meat of Tony's ass and slamming their bodies together while Tony moaned and begged for more. Tony came _again_ , eyes wide with startlement, and then he slumped down onto Steve and groaned.

"Want me to stop?" Steve murmured, and Tony shook his head.

"Hell no. Give me a second... God, this is fantastic."

Steve got an arm around his waist and rolled them over. Tony was deliciously supple, hooking one leg up over Steve's shoulder and wrapping the other round his waist, opening himself wide so Steve could fuck him even deeper. Even this close, there were no creases round his eyes. Steve missed the laughter lines. Still, the way he licked his lips and fixed Steve with hazy blue eyes was just the same, and Steve braced one arm on the bed and held Tony's hip with the other and set out to pound Tony into the mattress.

"Jesus fuck," and the arch of Tony's back brought back delicious memories, the way he struggled against Steve's grip. He was hard again already, trying to rub up against Steve's belly and push down onto his cock at the same time, but Steve was merciless, made him just take it, and God that felt good, Steve had missed being rough with him. He put more of his weight on Tony, pinned him, and then shifted his weight to his elbow and pushed his fingers into Tony's mouth.

"Suck me," he breathed, and concentrated on grinding as deep as he could while Tony moaned around his fingers, using too much teeth and drooling onto the pillow. He loved it when Tony lost it, when all that finesse and skill was stripped away and Tony was just an animal for it -

He bit too hard when he came, knotted a hand in Steve's hair and yanked, and then made a noise of dizzy wonder and looked down at his dick, still hard.

"Huh," Steve rolled his hips faster, and Tony tried to speak but choked on his own breath. In under two minutes he was coming again, whimpering with the force of it. Steve considered a technovirus designed by people with the Stark name; he braced his knees more firmly and settled in for the long haul.

 

Steve managed to lose track of time in there somewhere, and he'd certainly lost count of how many times Tony had come. He looked completely shattered; Steve nuzzled into his grey hair and wondered how often they could do this. The feeling of delicious, worn-out satisfaction that seeped through his bones was definitely something he wanted as often as possible.

"Jeeeeessus," Tony reached for his phone, and Steve frowned at him as his thumbs moved over the screen. The Extremis again, no doubt; a normal person would have been a limp noodle for a while. "Ha!"

"What are you doing?" Steve reached for the phone and Tony wriggled away and nipped at his fingers.

"Just letting Gregory know. Multiple orgasms, my God. Extremis is the best thing ever."

"Don't - you can't tell him - "

"We've been married almost forty years, I think he knows we fuck."

"But - "

"Anyway, it's science."

The phone beeped, accusingly, and Tony giggled at whatever message had appeared on the screen. Steve sighed, and closed his eyes.

Yes, he could get used to this.

**Works inspired by this one:**

  * [Touch Me, I Wanna Be Dirty](https://archiveofourown.org/works/272086) by [blue_jack](https://archiveofourown.org/users/blue_jack/pseuds/blue_jack)




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